JPH0126867B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a laminate, and more particularly to a laminate suitable for sheet forming. Currently, the sheet forming method is often used to produce containers such as cups and trays for food packaging because the equipment costs are low and molding is easy. In this sheet forming method, polystyrene is mainly used as the sheet material because of its good formability. In recent years, resin containers such as cups and trays are required to have barrier properties as the contents become more diverse. The object of the present invention is to provide a polystyrene layer and an ethylene-
An object of the present invention is to provide a laminate having a saponified vinyl acetate copolymer layer. By drawing the laminate of the present invention into sheets, food packaging containers such as cups and trays having high barrier properties can be obtained. By the way, the present inventor has considered various methods for laminating polystyrene and saponified ethylene-vinyl acetate copolymer. This method attempts to laminate one or more resin composition layers and laminate them by thermal bonding or coextrusion. However, in the method of laminating polystyrene and saponified ethylene-vinyl acetate copolymer using an adhesive, there are problems in that the adhesive layer peels and the layer breaks during deep drawing. It is something that is not desirable. Furthermore, even in the methods of laminating one or more resin composition layers and thermally adhering or coextruding them, there is no method that can obtain sufficient adhesive strength, and delamination occurs when deep drawing is performed. As a result of further studies on the above-mentioned problems, the present inventor found that styrenic resins with 10% to 80% by weight
and vinyl acetate content of 5% to 50% by weight.
10% by weight of ethylene-vinyl acetate copolymer resin
An adhesive composition comprising 10 to 80% by weight of a polyolefin obtained by graft-polymerizing 80% by weight of polystyrene and an ethylenically unsaturated monomer having a carbonyl group is used.
Strongly heat-bonded saponified vinyl acetate copolymer,
When polystyrene and saponified ethylene-vinyl acetate copolymer were coextruded into a sheet using the adhesive composition, it was discovered that the three layers were strongly adhered, and based on this knowledge, the present invention was completed. This is what I did. The above-mentioned present invention will be explained in more detail below. First, to explain the layer structure of the laminate of the present invention, the laminate of the present invention, as shown in FIG.
Polystyrene layer 1, styrene resin 10% by weight
80% by weight and vinyl acetate content 5% to 80% by weight
Weight% ethylene-vinyl acetate copolymer resin 10
An adhesive composition layer (hereinafter referred to as "adhesive") is made by blending a polyolefin obtained by graft polymerizing an ethylenically unsaturated monomer having a carbonyl group in a proportion of 10 to 80% by weight with an ethylenically unsaturated monomer having a carbonyl group. 2 and a saponified ethylene-vinyl acetate copolymer layer with an ethylene content of 20 to 50 mol% and a degree of saponification of 90% or more (hereinafter referred to as the "saponified layer")
It consists of a structure in which three layers (No. 3) are sequentially laminated. Alternatively, to show another form of the laminate of the present invention, as shown in FIG. 2, like the laminate shown in FIG. 1 above, a polystyrene layer 1,
A laminate consisting of five layers, in which an adhesive composition layer 2 and a saponified material layer 3 are sequentially laminated, and an adhesive composition layer 2 and a polystyrene layer 1 are further sequentially laminated on the saponified material layer 3. It may be hot. That is, in the laminate of the present invention, three layers: a polystyrene layer, an adhesive composition layer, and a saponified layer
The basic structure is that the layers are stacked sequentially,
A layer of the same or other resin may be optionally laminated thereon. As the polystyrene constituting the polystyrene layer in the above invention, for example, GP polystyrene, high impact styrene, medium impact polystyrene, etc. can be used. In addition, examples of the styrene resin constituting the adhesive composition layer in the present invention include polystyrene, styrene-butadiene copolymer resin, acrylonitrile-styrene copolymer resin, styrene-butadiene-acrylonitrile copolymer resin, and acrylate-styrene-acrylonitrile. copolymer resin,
A methacrylate-butadiene-styrene copolymer resin, a styrene-isoprene copolymer resin, or the like can be used. Next, in the present invention, the ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 5% to 50% by weight, constituting the adhesive composition layer, can be prepared by, for example, a known free catalyst polymerization method. Those obtained by polymerization can be used. Furthermore, in the present invention, the polyolefin graft-polymerized with an ethylenically unsaturated monomer having a carbonyl group constituting the adhesive composition layer can be obtained by, for example, a graft reaction method in a solution state (for example, Japanese Patent Publication No. 44-15422). (see Japanese Patent Publication No. 1987), a method of grafting in a molten state (for example,
27421), other methods in which the graft reaction is carried out in a slurry state, and methods in which the graft reaction is carried out using heat and shear force in a kneader (for example,
18522) can be used. Examples of the ethylenically unsaturated monomer having a carbonyl group in the present invention include carbonyl based on carboxylic acid, carboxylate, carboxylic acid anhydride, carboxylic acid ester, carboxylic acid amide or imide, aldehyde, ketone, etc.

[Formula] Group alone or cyano (-C≡N) group; hydroxy group; ether group; oxirane

[Formula] One type or a combination of two or more types of ethylenically unsaturated monomers having a ring etc. can be used, and suitable examples thereof are as follows. A Ethylenically unsaturated carboxylic acid: acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, 5-norbornene-2,3-dicarboxylic acid, etc. B Ethylenically unsaturated carboxylic anhydride: maleic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, tetrahydrophthalic anhydride, etc. C Ethylenically unsaturated esters: ethyl acrylate, methyl methacrylate, 2-ethylhexyl acrylate, mono- and di-ethyl maleate, vinyl acetate, vinyl propionate, propyl γ-hydroxy methacrylate,
β-hydroxyethyl acrylate, glycidyl acrylate, glycidyl methacrylate, β
-N-ethylaminoethyl acrylate, etc. D Ethylenically unsaturated amide or imide: acrylamide, methacrylamide, maleimide, etc. E. Ethylenically unsaturated aldehydes or ketones: acrylolein, methacrolein, vinyl methyl ketone, vinyl butyl ketone, etc. In the present invention, among the above-mentioned monomers,
Ethylenically unsaturated carboxylic acids or ethylenically unsaturated carboxylic anhydrides are particularly preferred, and these monomers are used alone or in combination with other monomers. In addition, as the polyolefin in the present invention, polyethylene, ethylene-α-olefin copolymer, polyα-olefin such as polypropylene, polybutene, polyisobutylene, polydiolefin such as polybutadiene, polyisoprene, or copolymers thereof, etc. are used. can do. In addition, the adhesive composition layer in the present invention is composed of a styrene resin of 10% to 80% by weight and an ethylene-vinyl acetate copolymer resin with a vinyl acetate content of 5% to 50% by weight of 10% to 80% by weight. From 10% by weight of polyolefin made by graft polymerization of and an ethylenically unsaturated monomer having a carbonyl group.
When the styrene resin content is 80% by weight or less, the adhesive strength between the adhesive composition layer and the polystyrene layer becomes weak, and when it exceeds 80% by weight, the adhesive strength of the adhesive composition layer becomes weak. Film-forming properties become extremely poor, and for this reason, styrene-based resins are reduced from 10% by weight.
80% by weight is preferred. In addition, vinyl acetate content 5
If the amount of ethylene-vinyl acetate copolymer resin is 10% by weight or less, the adhesive strength between the adhesive composition layer and the polystyrene layer will be weak, and if the amount is 80% by weight or more, the adhesive strength will be weak between the adhesive composition and the polystyrene layer. The adhesion of the compound layer becomes weaker, and therefore 10% to 80% by weight is preferred. In addition, if the polyolefin graft-polymerized with an ethylenically unsaturated monomer having a carbonyl group is less than 10% by weight, the adhesive strength between the adhesive composition layer and the saponified layer becomes weak, and if it exceeds 80% by weight, the adhesive composition The adhesion between the material and the polystyrene layer becomes weaker, and therefore the content is preferably 10% by weight to 8% by weight. Next, in the above invention, the ethylene content constituting the saponified layer is 20 to 50 mol%, and the degree of saponification is 90.
% or more of saponified ethylene-vinyl acetate copolymer can be used. In the present invention, if the ethylene content is less than 20 mol%, there is no moisture resistance or water resistance, and if the ethylene content is less than 20 mol%, If the ethylene content exceeds 20%, the barrier properties will decrease.
50 mol% is good. Also, if the degree of saponification is less than 90%, the barrier properties will deteriorate, so the degree of saponification must be 90% or more. Furthermore, in the present invention, other resins that can be further laminated in addition to the three layers of the polystyrene layer, adhesive composition layer, and saponified layer include:
For example, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-
Saponified vinyl acetate copolymer, ethylene-α-olefin copolymer elastomer, styrene-butadiene-acrylonitrile copolymer, styrene-
Resins such as acrylonitrile copolymer, polyamide, polycarbonate, polysulfone, polyacetal, polymethyl methacrylate, polyphenylene oxide, polyurethane, polyethylene terephthalate, and polybutylene terephthalate can be used in a single layer or in combination. Next, the method for manufacturing the laminate of the present invention will be explained. There are various methods for manufacturing the laminate, for example, a polystyrene layer, an adhesive composition layer,
and three types of resin sheets or films constituting each layer of the saponified material layer, and then heating the three,
A method of thermally bonding the three layers by applying pressure, or a method of extruding the resins constituting each layer of the adhesive composition layer and the saponified material layer to create a coextruded film, and then forming a polystyrene layer with the film. There are methods such as thermally bonding polystyrene. In addition, the heating method in the present invention includes heat treatment using an induction heating roll, heat treatment by blowing hot air with a dryer, heat treatment using flame, etc. Heat treatment is performed at a temperature of 80°C to 300°C, preferably 120°C to 250°C. It is recommended to apply Further, in the present invention, the laminate shown in FIG. 2 can be manufactured by, for example, a coextrusion method. In that case, the temperature required to extrude the coextruded sheet is 150℃ to 250℃.
and preferably 180°C to 240°C. In addition, in the laminate according to the present invention, the layer structure has a basic three-layer structure of a polystyrene layer, an adhesive composition layer, and a saponified layer, and another layer can be optionally provided in addition to this, in this case,
The layers can be laminated by any method such as a lamination method using a common adhesive or an extrusion lamination method. In the present invention, the method of draw-forming the laminate (sheet forming method) includes, for example, a vacuum forming method, a pressure forming method, a vacuum pressure forming method, and the like. Alternatively, a form, film, seal method (FFS method), which involves forming, filling, sealing, and cutting, may be used. Thus, the laminate obtained according to the present invention has a polystyrene layer and a saponified layer, and an adhesive composition layer 1.
It is possible to provide a resin container such as a cup or a tray that can be strongly bonded only through the layers, has good drawability, and has high barrier properties without causing delamination during molding. In addition, this resin container has good smoothness on the outer and inner surfaces of the container, and can be used for miso, soy sauce, desserts, youth, margarine, etc., which require high barrier properties.
It can be used in a variety of ways, such as containers for packaging foods such as butter and alcoholic beverages, and containers for packaging drugs. Next, the present invention will be described in more detail with reference to Examples. Example 1 800μ high impact polystyrene sheet,
Styrenic polymer resin (Tuffrene A manufactured by Asahi Kasei Corporation) with a melt index of 2.6 g/10 minutes and a specific gravity of 0.95 20% by weight and ethylene-vinyl acetate copolymer with a vinyl acetate content of 28% by weight and a melt index of 18 g/10 minutes. Laminated 30μ of a composition film made by blending 30% by weight of resin and 50% by weight of low-density polyethylene graft-polymerized with a melt index of 1.8 g/10 minutes and 0.3% by weight of maleic anhydride added with a specific gravity of 0.905. Furthermore, 17μ of saponified ethylene-vinyl acetate copolymer film (ethylene content 30 mol%, saponification 99.2%) was laminated and thermally bonded by passing it through a Teflon-coated induction heating roll (temperature 190°C). (Figure 1). When the adhesive strength between each layer of this three-layer laminate was measured, the adhesive strength between the polystyrene layer and the composition layer was
The adhesive force between the composition layer and the saponified material layer was as strong as 1,100 gw/15 mm width and 1,300 gw/15 mm width. Example 2 Melt flow index 10.5g/10min, specific gravity
1.04 high impact polystyrene (Nippon Steel Chemical Co., Ltd., Estyrene H-60) is used as the polystyrene layer, melt index 2.6g/10 minutes specific gravity 0.95
Styrenic polymer resin (Asahi Kasei Kogyo, Tuffrene A) 20% by weight and vinyl acetate content 28% by weight,
Low-density polyethylene resin 50 graft-polymerized with 30% by weight ethylene-vinyl acetate copolymer resin with a melt index of 18 g/10 minutes and 0.3% by weight of maleic anhydride with a melt index of 1.8 g/10 minutes and a specific gravity of 0.905. % by weight was used as the adhesive composition layer, and a saponified ethylene-vinyl acetate copolymer with an ethylene content of 33 mol% and a degree of saponification of 99.5 mol% was used as the saponified material layer, as shown in Figure 2. Extrusion sheet molding was performed. The thickness of each layer is 500 μm for the polystyrene layer, 30 μm for the composition layer, and 30 μm for the saponified layer.
The extrusion temperature was 200°C. When we measured the adhesive strength between each layer of this coextruded sheet, we found that the adhesive strength between the polystyrene layer and the composition layer was
The adhesive strength between the composition layer and the saponified material layer was 1200 gw/15 mm width. Further, the sheet was subjected to deep drawing and pressure forming, but no peeling between layers or film breakage occurred, and the forming condition was good. Example 3 800μ high impact polystyrene sheet 1
, melt index 2.6g/10 minutes, specific gravity 0.95
Styrenic polymer resin (manufactured by Asahi Kasei Kogyo, Tuffrene A) 20% by weight, vinyl acetate content 28% by weight, melt index 18g/10 minutes of ethylene.
An adhesive made by blending 30% by weight of a vinyl acetate copolymer resin and 50% by weight of a low-density polyethylene resin graft-polymerized with a melt index of 1.8 g/10 minutes and an addition amount of maleic anhydride of 0.3% by weight with a specific gravity of 0.905. A 20 μm layer of the agent composition film 2 was laminated, and a saponified ethylene-vinyl acetate copolymer film 3 was further layered.
(ethylene content 30 mol%, saponification degree 99.2%) 17μ
Laminated, melt index 1.8g/10 minutes,
A 20μ low-density polyethylene resin film 4 graft-polymerized with a specific gravity of 0.905 and an added amount of maleic anhydride of 0.3% by weight was laminated, and Saranex 265
(trade name manufactured by Asahi Dow Co., Ltd., 64μ thick polyethylene/polyvinylidene chloride/polyethylene laminate) was laminated and thermally bonded by passing it through a Teflon-treated induction heating roll (temperature: 190°C) (Figure 3). ). When the adhesive strength between each layer of this laminate was measured, the adhesive strength between the polystyrene layer and the adhesive composition layer was
1300gw/15mm width, the adhesive strength between the adhesive composition layer and the saponified material layer is 1200gw/15mm width, the saponified material layer and the low density polyethylene layer grafted with maleic anhydride cannot be separated; It was impossible to separate the low-density polyethylene layer graft-polymerized with Saranex 26. Further, the sheet was subjected to deep-drawing pressure forming, but no peeling between layers or film breakage occurred, and the forming condition was good.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the layer structure of the laminate of the present invention, and FIGS. 2 and 3 are sectional views showing the layer structure of another form of the laminate of the invention. 1... Polystyrene layer, 2... Adhesive composition layer, 3... Saponified material layer.

Claims (1)

[Scope of Claims] 1. Polystyrene layer, styrene resin 10% to 80% by weight and vinyl acetate content 5% to 80% by weight.
50% by weight ethylene-vinyl acetate copolymer resin
An adhesive composition layer containing 10% to 80% by weight of a polyolefin graft-polymerized with an ethylenically unsaturated monomer having a carbonyl group in a proportion of 10% to 80% by weight, and an ethylene content.
A laminate in which three saponified ethylene-vinyl acetate copolymer layers having a saponification degree of 20 to 50 mol% and a saponification degree of 90% or more are laminated in the above order. 2 Polystyrene layer, from 10% by weight of styrene resin
80% by weight and vinyl acetate content 5% to 50% by weight
Weight% ethylene-vinyl acetate copolymer resin 10
Adhesive composition layer comprising 10% to 80% by weight of polyolefin graft-polymerized with an ethylenically unsaturated monomer having a carbonyl group and 10% to 80% by weight, ethylene content 20 to 80% by weight. 50
A laminate in which five layers are laminated in the above order: a saponified ethylene-vinyl acetate copolymer layer with a mole % saponification degree of 90% or more, the above adhesive composition layer, and the above polystyrene layer.